1. Field of the Invention
The invention pertains to medical devices for fluids, more particularly syringes with a retraction feature.
2. Background of the Prior Art
The syringe art has advanced rapidly in recent years because of the threat of AIDS and other infectious diseases and the inevitability of accidental needle sticks suffered by healthcare providers from the use of needles on infected patients. Used syringes with extended needles present a risk to medical personnel and sanitation employees and other in the disposal chain.
Most of the prior art retractable syringes are theoretical devices only which have never reached the market because of various practical deficiencies. These practical deficiencies relate to complexity, reliability, repeatability, cost and ease of use. Syringes must be mass produced at the rate of millions per day. Cost is a significant factor in manufacture of the parts and the assembly of the device. Automated production of parts and assembly of parts is critical in order to have any hope of supplying a practical syringe to the market. A significantly improved retractable syringe is disclosed in my U.S. Pat. No. 5,385,551, the disclosure of which is incorporated herein by reference.
In a curious development, healthcare workers in the drug control field have expressed a need for a reusable retractable syringe to prevent the spread of AIDS. Such a syringe is preferably a full displacement syringe which will deliver essentially all of the contents without retracting and without limiting the ability of the user to draw a second dose. Hopefully the drug user will confine use to himself without sharing the needle but can retract the needle when finished and render the device inoperable.
There is also a need for a multiple use retractable syringe for diabetics to use at home to inject insulin, where AIDS is not a factor. After a day's use, for instance, the home user can retract the syringe to prevent any risk to others in the disposal chain. All this is to be accomplished without affecting the ability of professional healthcare workers from injecting a dose into a patient and then initiating retraction and non-reusability while the needle is still in the patient's arm. In all embodiments, retraction renders the syringe non-reusable. The present invention is designed to accomplish these goals and more.